You should definitely specify which game/engine you're working with, as that process will be different in all of them. Fortunately, I know which one you're using (mine ;3).
Here's what you gotta do:
Code:
local c = actor[newActor(Thing, x, y)]
This lets you store a direct reference to the newly-created instance, instead of having to write something like `actor[id]` every time. It will still be added to the global actors list as normal, and since you're using a local, the reference will be deleted as soon as you're done working with it automatically, allowing the instance manager to clean it up properly. Now, you can reference its properties like so:
Code:
local c = actor[newActor(Thing, x, y)]
newActor(SolidThing, c.x, c.y)
I hope this helps!